1. Field of the Invention
The present invention relates to an improved annular seal assembly which has particular application to sealing across annular spaces between facing cylindrical surfaces, such as the annular seal between the exterior of a hanger and the surrounding housing in a well.
2. Description of the Related Art
Prior annular seal assemblies have used annular seals having a U-shaped section with expander rings positioned in the space between the two legs of the ring to, either mechanically or in response to pressure, urge the expander ring inwardly of the legs to wedge the legs outward into sealing engagement with the facing cylindrical surfaces to effectively seal across the annulus between such surfaces.
U.S. Pat. No. 3,288,472 to B. J. Watkins discloses a metal seal which includes a U-shaped ring having legs extending axially away from an annular base and tapering outwardly at an angle preferred to be approximately 2.degree.. This provides an interference fit for the legs of the seal ring with respect to the surfaces against which they are to seal. U.S. Pat. Nos. 3,378,269; 4,766,956; and 5,031,923 all disclose similar metal seals which include annular metal seal rings having a U-shaped section and having an interference fit with the surfaces against which they are to seal.
U.S. Pat. No. 2,075,947 discloses a pipe joint which includes a soft metal seal ring having a pair of upwardly extending spaced legs and a pair of downwardly extending spaced legs with an annular hard metal wedging member positioned between each pair of legs and energized by the nut to be forced between the legs to urge the legs radially into sealing engagement with the outer and inner annular cylindrical surfaces against which they are to seal. Other prior art patents disclosing similar structures include U.S. Pat. Nos. 3,915,462; 2,766,956; 4,900,041 and 5,044,672.
U.S. Pat. No. 3,326,560 to M. D. Trbgovich discloses an adjustable annular seal which has a V-shape and includes a split ring expander positioned between the diverging legs of the seal ring with suitable shoulders containing and urging the seal ring and expander together so that the expander urges the legs of the seal ring radially into sealing engagement with the annular walls against which it is to seal. The expander is described as being substantially coextensive in length with the sealing ring and being resiliently compressible for urging the walls (legs) apart to compensate for wear of the sealing portions. It is stated that the expander should be constrained from moving into engagement with the sealing surfaces and thus should not act as a sealing element itself. It should be noted that this patent specifically suggests the use of a split ring as the expander, it does not suggest any particular advantages. It could be that the advantage was that it was easier to install than a solid ring since it had to be assembled within the seal ring and in the space bounded by the sealing surfaces and the shoulders which urge the expander into the seal ring so that its sealing legs are urged toward the sealing surfaces.
The Lee Company manufactures hydraulic inserts or plugs which are adapted to be inserted into an opening to close and seal the opening. The Lee plug is cylindrical with a tapered reamed hole part way through its center and numerous small grooves in its exterior surface. It is used with a tapered reamed hole part way through its center and numerous small grooves in its exterior surface. It is used with a tapered pin which is driven into the reamed hole until the plug and the pin are flush with each other. The pin wedges the tapered sides of the plug into biting engagement with the surrounding material forming independent seals and retaining rings. This plug does not have any use for sealing across an annulus.